A tree stake (as was pointed out by Gabriele Sanio in the latest newsletter of the Garden and Landscape Designers Association) should not be an eyesore. It should not compete with the tree for your attention. So, if you're planting trees now (there's still plenty of time) use a tree stake about a metre long, and don't let more than about a third of it protrude above soil level.
Before the garden starts into growth again, check existing tree, shrub, and climber-ties to make sure they are secure, but not so tight that they may strangle their host. Trellises, pergolas and other garden structures should be maintained now, while you can still get at them easily.